Generally a hearing aid system according to the invention is understood as meaning any system which provides an output signal that can be perceived as an acoustic signal by a user or contributes to providing such an output signal, and which has means which are used to compensate for an individual hearing loss of the user or contribute to compensating for the hearing loss of the user or contribute to compensating for the hearing loss. These systems may comprise hearing aids which can be worn on the body or on the head, in particular on or in the ear, and can be fully or partially implanted. However, some devices whose main aim is not to compensate for a hearing loss, may also be regarded as hearing aid systems, for example consumer electronic devices (televisions, hi-fi systems, mobile phones, MP3 players etc.) provided they have, however, measures for compensating for an individual hearing loss.
Within the present context a hearing aid may be understood as a small, battery-powered, microelectronic device designed to be worn behind or in the human ear by a hearing-impaired user. Prior to use, the hearing aid is adjusted by a hearing aid fitter according to a prescription. The prescription is based on a hearing test, resulting in a so-called audiogram, of the performance of the hearing-impaired user's unaided hearing. The prescription is developed to reach a setting where the hearing aid will alleviate a hearing loss by amplifying sound at frequencies in those parts of the audible frequency range where the user suffers a hearing deficit. A hearing aid comprises one or more microphones, a battery, a microelectronic circuit comprising a signal processor, and an acoustic output transducer. The signal processor is preferably a digital signal processor. The hearing aid is enclosed in a casing suitable for fitting behind or in a human ear. For this type of traditional hearing aids the mechanical design has developed into a number of general categories. As the name suggests, Behind-The-Ear (BTE) hearing aids are worn behind the ear. To be more precise, an electronics unit comprising a housing containing the major electronics parts thereof is worn behind the ear, and an earpiece for emitting sound to the hearing aid user is worn in the ear, e.g. in the concha or the ear canal. In a traditional BTE hearing aid, a sound tube is used to convey sound from the output transducer, which in hearing aid terminology is normally referred to as the receiver, located in the housing of the electronics unit and to the ear canal. In some modern types of hearing aids a conducting member comprising electrical conductors conveys an electric signal from the housing and to a receiver placed in the earpiece in the ear. Such hearing aids are commonly referred to as Receiver-In-The-Ear (RITE) hearing aids. In a specific type of RITE hearing aids the receiver is placed inside the ear canal. This category is sometimes referred to as Receiver-In-Canal (RIC) hearing aids. In-The-Ear (ITE) hearing aids are designed for arrangement in the ear, normally in the funnel-shaped outer part of the ear canal. In a specific type of ITE hearing aids the hearing aid is placed substantially inside the ear canal. This category is sometimes referred to as Completely-In-Canal (CIC) hearing aids. This type of hearing aid requires an especially compact design in order to allow it to be arranged in the ear canal, while accommodating the components necessary for operation of the hearing aid.
Within the present context a hearing aid system may comprise a single hearing aid (a so called monaural hearing aid system) or comprise two hearing aids, one for each ear of the hearing aid user (a so called binaural hearing aid system). Furthermore the hearing aid system may comprise an external device, such as a smart phone having software applications adapted to interact with other devices of the hearing aid system, or the external device alone may function as a hearing aid system. Thus within the present context the term “hearing aid system device” may denote a traditional hearing aid or an external device.
It is well known within the art of hearing aid systems that the optimum setting of the hearing aid system parameters may depend critically on the given sound environment. It has therefore been suggested to provide the hearing aid system with a multitude of complete hearing aid system settings, often denoted hearing aid system programs, which the hearing aid system user can choose among, and it has even be suggested to configure the hearing aid system such that the appropriate hearing aid system program is selected automatically without the user having to interfere. One example of such a system can be found in U.S. Pat. No. 4,947,432.
This general concept of automatically selecting the appropriate hearing aid system program requires that any given sound environment can be identified as belonging to one of several predefined sound environment classes. Methods and systems for carrying out this sound classification are well known within the art.
In order to provide the best possible sound quality and speech intelligibility in a hearing aid system it is important that the available dynamic range of the hearing aid system matches the dynamic range of the sound pressure level in the sound environments that a hearing aid system user experiences. However, for some types of microphones and analog-digital converters it is not possible to match the requirements to the available dynamic range in certain sound environments.
It is therefore a feature of the present invention to provide a method of operating a hearing aid system that improves the effective dynamic range of the hearing aid system.
It is another feature of the present invention to provide a hearing aid system adapted to improve the effective dynamic range of the hearing aid system.